1. Field of the Invention
The present invention relates to a process for preparing a di(fluoroalkyl containing group-substituted alkyl) phosphate salt.
The di(fluoroalkyl containing group-substituted alkyl) phosphate salt is useful as a surface active agent, a water- and/or oil-repellent for fiber or paper or an oil resistant agent.
2. Description of the Related Art
Processes for preparing fluoroalkyl containing group-substituted alkyl phosphate esters are disclosed in, for example, Japanese Patent Publications Nos. 7776/1979, 29875/1981 and 48158/1982 and Japanese Patent Kokai Publication No. 64990/1985.
However, the phosphate esters which are obtained by the above processes have wide distribution of composition which contains two or three of a monoalkyl ester, a dialkyl ester and a trialkyl ester. Of these three esters, the di(fluoroalkyl containing group-substituted alkyl) phosphate ester has the highest oil resistance, but is not produced in a high selectivity and contains relatively large amounts of monoalkyl and trialkyl esters. A yield of dialkyl esters is at most about 80% by weight, as described in Examples of Japanese Patent Publication No. 7776/1979. It is desired to increase the selectivity of dialkyl esters.